FACILITIES AND SERVICES

The 11.75 T narrow bore 54 mm Ultrashield magnet (500 MHz for ¹H) equipped with a Bruker Avance III console, with 3 RF Channels, BLAX H2H300/100/150 W Frequency Amplifier 200-600 MHz with 100 W for ¹H/¹⁹F, 150 W for ²H and 300 W for Broad Band Low Frequency, BLAX 300 W 6-365 MHz Broad Band Low Frequency Amplifier 6-350 MHz. This magnet also has four preamplifiers HPPR/2, three probe heads, 5 mm dual Z-Grad PA BBO BBF-H-D-05 Z, 1.7 mm microprobe Z-Grad PA TXI H/C-N-F-01.7 Z BTO and 4 mm HRMAS 15 kHz probe head (¹H, ¹³C/¹⁵N, ²H) with lock for semi solid samples, MAS-II unit system, BVT3000 temperature control unit, BOSS 3 Shimming System, BSMS/2 Lock System with 5 W transmitter amplifier for ²H, GAB unit 50 G cm^-1 Gradient for Z direction, DRU/E Digitizer Unit, pneumatic antivibration damping system and Bruker Sample Express Lite with 16 holders positions.

The 9.4 T narrow bore 54 mm Ultrashield magnet (400 MHz for ¹H) is equipped with a Bruker Avance III HD console, with 2 RF Channels, BLAXH 500/100 W 200-600 MHz with 100 W for ¹H/¹⁹F, and 500 W Broad Band Low Frequency. This magnet also has three preamplifiers HPPR/2, one probe head 5mm dual Z-Grad PA BBO BBF-H-D-05 Z, VTU temperature control unit, BOSS 3 Shimming System, BSMS/2 Lock System with a 5 W transmitter amplifier for ²H, GAB unit 50 G cm^-1 Gradient for Z direction, DRU/E Digitizer Unit, QNP Switch unit and BACS 16 sample exchanger.

The 4.7 Tesla narrow bore 54 mm not shielded magnet (200 MHz for ¹H) is equipped with Bruker DPX console, with 2 RF Channels, BLAXH 300/100 W E 6-365 MHz Frequency Amplifier 200-600 MHz with 100 W for ¹H/¹⁹F, and 300 W Broad Band Low Frequency. This magnet also has three preamplifiers HPPR/2, one probe head 5 mm BBI H-X-D, one 5 mm BBO X-H-D, BOSS 1 Shimming System, BSMS/2 Lock System with 5 W transmitter amplifier for ²H and SADC+ Digitizer Unit.

X-ray Photoelectron Spectroscopy (XPS)

The XPS facility operates a ThermoFisher Scientific spectrometer, model ESCALAB 250Xi, comprising the additional techniques: ultra-violet photoelectron spectroscopy (UPS), ion scattering spectroscopy (ISS), and reflected electron energy loss spectroscopy (REELS).

X-Ray Photoelectron Spectroscopy (XPS) measurements are performed with a monochromatized Al Kα (hν = 1486.6 eV) radiation source, operated at 216 W and a hemispherical electron energy analyzer under pressure below 5x10^-9 mbar. The binding energy scale is periodically calibrated using the Au4f7/2 line at 84.0 eV and the main features are: resolution around 0.6 eV and an error range for the binding energy of ±0.2 eV; ultimate elemental detectability of 0.07 at.% and analysis depth about 10 nm. The XPS analysis applies to solid, dry samples that are resistant to the ultra-high vacuum environment and direct X-ray incidence.

UPS measurements use a He discharge lamp that emits two specific energies, known as He I (21.21 eV) and He II (40.8 eV) lines. UPS analysis applies mainly to additional material investigation for determining the valence band structure and work function of materials, relevant parameters mainly for semiconductors in general.

REELS measurements are obtained from the kinetic energy analysis of reflected electrons from the surface after inelastic collisions. REELS analyses are applied to the study of electronic transitions of materials and allow inferring about the electronic gap.

X-Ray Diffractometry (DRX)

The X-ray facility operates a Rigaku X-ray diffractometer, model Ultima IV (Cu Kα 0.1542 nm), with a fixed power source (40 kV, 20 mA), with an ultra-fast detector (model D/Tex Ultra 250 1D silicon tape) and Ni filter, able of scanning from 2 to 150⁰. Samples can be analyzed ex situ at room temperature in standard or spinning accessories, or in situ in a temperature chamber operating in the 25 ⁰C to 1500 ⁰C range, in vacuum, helium or mixture of hydrogen with other gases (concentrations below ≈ 5%). The crystalline phases can be identified through the existing database in the PDXL program.

X-Ray Fluorescence

The XRF facility comprises a Bruker S8 Tiger and a WDXRF Rigaku Supermini 200R spectrometers. This facility allows for qualitative and semi-quantitative identification of the atomic composition of solids, liquids, powders, alloys and thin films samples containing elements with atomic number ≥ 8 (O to U).

Computing Facilities

Several theoretical oriented research groups have computer clusters and servers which are primarily for use of their students but arrangements are usually possible to make these facilities available to other students.

Villa-Lobos is a SGI Altix ICE 8200LX server comprising 25 blade nodes of 2 Intel Xeon Quad-core LLSS20 processors and 2 infiniband switches. Server Bach is a home-made assembled cluster with different types of processors, presently comprising 280 cores.

Computing facilities are also provided by the Brazilian National Laboratory for Scientific Computing (see off-campus facilities).

HOME-MADE Instruments

The faculty members of the PGQu have a long tradition of building their own instruments, some of them not commercially available, as the ones presented below.

Electron Stimulated Ion Desorption Spectrometer

This instrument was built and optimized for the detection of ionic fragments (positive and negative) and neutral species of compounds in solid/condensed phase, when irradiated with high energy electron beam. The system comprises a chamber in ultra-high vacuum (UHV – 10^-9 Torr) containing a time-of-flight mass spectrometer (TOF-MS), also projected and constructed in-house, a commercial quadrupolar type mass spectrometer for the detection of ions and analysis of residual gases from the vacuum chamber and neutral species, an electron gun with adjustable energy (between 150 and 1000 eV), which can work either in continuous or pulsed mode, and a manipulator of samples (XYZ). The UHV system consists of a mechanical pump, a turbomolecular pump and a titanium sublimation pump to keep the vacuum required to carry out the experiments.

Variable-Angle Electron Energy-Loss Spectrometer

The electron energy-loss spectrometer was designed and built to allows for the experimental determination of excitation energies and oscillator strengths for atomic and molecular electronic transitions occurring in the 2 – 100 eV energy range (from the visible up to the vacuum ultraviolet spectral range). The large angular range (1 – 20⁰) and high incident energy (200 – 2000 eV) make possible the observation of both dipole-allowed and quadrupole-allowed electronic transitions.

OFF-Campus Facilities

The PGQu theoretical oriented groups may have access to the computing facilities of the Brazilian National Laboratory for Scientific Computing. LNCC is equipped with a ATTOS-BULL supercomputer with 36.472 cpu distributed over 1134 nodes and a peak performance of 5.1 PF. For more details see https://sdumont.lncc.br/

The Brazilian Synchrotron Light Laboratory (LNLS) operates the only synchrotron light source in Latin America and offers an extremely sophisticated infrastructure for academic and industrial researchers. Many of the PGQu research groups conducting research in spectroscopy and materials chemistry make use of the LNLS facility. For more details see https://www.lnls.cnpem.br/en/